1. Field of the Invention
This invention relates to semiconductor devices and particularly to erasable programmable flash memory devices.
2. Description of Related Art
Holes induced by source erase cause a reliability problem in Flash memory devices. Although use of negative gate source erase alleviates hot hole injection, the problem is that it does not eliminate hot hole generation.
U.S. Pat. No. 5,395,773 of Ravindhran et al. shows a MOSFET with a gate penetrating halo implant. However, the halo implant is below the source/drain (S/D) regions and is for a different purpose from the halo ion implant of the invention.
U.S. Pat. No. 5,364,807 of Hwang how to modify an N-type Lightly Doped Drain/source (LDD) structure by using a halo ion implant to form an inboard P-type halo region located both below the LDD region and beyond the LDD region in the channel region. The specific method steps and structure of Hwang contrast with the present invention. The Hwang method is to remove the spacer on one side of the gate electrode stack to expose the LDD region on that side for ion implantation of ions to form the inboard halo region.